Advanced Link And Association Concept

Advanced Link And Association Concept

link attributes

• an attribute is a property of the object in a class a link attributes is a property of the linked in an association
• in following figure access permission is an attribute of associate By.

• Following Shiva present link attributes for two minutes to one Association.each person working for a company receives a salary and have a job title the boss in the form of each worker

    Figure. Link attributes for one to many Association

• following figure shows link attributes for ternary associations of player me play for many terms in a given year

• Following figure shows link attributes various object attributes

Modelling an association as a class

• Sometime is useful to model and Association has a class
• Which link become one instance of the class
• the link attributes box is actually a special case of an association as a class and many have a name and operation in addition to attributes
• Following figure shows the authorisation information for users on workstation

Role names

• Role is a one end of an association
• Binary Association has two rows each of which many have a role names
• Role name is a name that equally identify one end of an association
• Rolls-Royce a way to weaving a binary Association as a travel from one object to a set of associated objects
• each roll on a binary Association identifiers and ostrich of objects associated with an object at the other end
• calling figure specified how person and company participate in Association worker for a person assume the role of employees with respect to a company a company has given the role of employers with respect to a person
• running is written next to Association line near the class that plays the role

• use of role name speech optional but is equals option is there and left considering considering to assign role names in state of or in addition to Association names
• role name are necessary for Association between two object of the same class for example boss and worker distribute the two employees participating in a managers Association

Ordering

• The organ is an inheritance part of the association
• the object at the many sides of an association the sometimes explicitly are there is for example following figure shows a workstations cream containing a number of overlapping Windows the windows are explicitly order it

• an ordered set of objects on the many and of association is indicated by writing or generate next to the multi city dot for the role
• This is a special kind of constraints

Qualification

• Qualifier associations related to object classes and a qualifier
• the qualifier is special attribute that relieves the effective multiplicity of an association
• One to many and many to many Association may be qualified
• The qualifier distinguish among the set of objects at the end of an association
• Qualified Association can also be considered as a form of ternary association
• For example in following figure a directory has many files of qualifier filename distinguishes of file missing a set of files contains in directory because a directory does not have two files with same name

• qualifier is grow as a small box on the end of association lying near the class is qualified directory + filename held a file therefore file name is missing in a box contagious to directory

Generalisation and inheritanc

• generation reforms to a relationship between general class superclass operating class and more specific version of the class to subclass of child class
• generation is a relationship between a class and more or more different version of 8th class b amplifier is called the superclass and acidified version is called a subclass
• 0for example Sheikh is a superclass a rectangle circle and polygon attributes are operation common to a group of subclasses are attached to the superclass and shared by itself class
• colouring figure shows a stage generalisation rectangle circle and polygon shape square is special kind of rectangle

Figure multilevel inheritance hierarchy

• subclass Americans the future of superclass as well it at one feature also for example circle inherits attributes origin circle colour and paint thickness from Sheikh and as a radius of its one
• Generalisation is a sometime called the is a relationship because is instance of subclass is an instance of the superclass as well
• the notation for general physician in OMG is a triangle connecting a superclass to each subclass the superclass is connected by a line to the attacks of the triangle the subclass are connected by line to horizontal bar attached to the base of rectangle

Use of generalisation

• generation is a useful for both conceptual modelling and implementation
• Generalism facility modelling by structuring classes and capturing what is similar and what is different amount classes
• inheritance of operational is useful during implementation as a vehicle for reducing code

Note:the term inheritance generalisation and specialisation reference to a same concept and after used interchangeably

Overriding feature

• subclass me for riding a superclass future by defining a future with the same name
• The overriding future the subclass feature define the replaces the over hidden feature the superclass feature
• for example in our figure display must be implemented separately for each kind of shape

Grouping constructs

Module

• Module is a logical construct for grouping classes associations and generalization
• for example admission library and payroll are different module for college management system
• an object model consists of one or more models models nw2 person and object model into manageable pieces
• Class name and Association name must be unique with a model
• the model name is usually listen and the top of each state there is no other special notation for module

Sheet

• Complex module will not speak on a single pieces of paper
• ostrich is mechanism for breaking a large object model down into a series of pages
• Acid is a single print page
• Each module consists of one or more sheets
• Each sheet has a title and name or number
• association and generalization appears on a single seat classes may appear on multilevel sheet

Aggregation

• Aggregation is just come from association in which of aggregate object is made of components components are part of aggregate
• aggregation is the park hotel or a part of relationship in which object reproductive of components after click are associated with an object represent in the entire assembly
• for example and name argument list and a component President are part of c language function definition which is turn is part of an entire program
• the most significant property of education is transistor with that if a is part of b and b is part of cdna is part of c
• average Aslam is also antique metric that is if a is part of b10 b is not part of a
• finally some properties of an assembly applicable to the components as well possibly with some modifications for example the field and location of a car door handle is obtained from the ore of which it is a parrot the door instead of date is properties from the car of which it is a part
• aggregation is down like Association accept a small diamond indicates the Assembly age of the relationship
• following figure shows a position of an object model for a word processing programming document consists of many paragraph each paragraph consists of many sentences

Figure aggregation

• The existence of a component object may depend on the existence of the aggregate object of which it is part.
• Following figure demostrates that aggregation may have number of levels. A computer is composed of one or more monitors, a system box, an optional, mpuse, and a keyboard. A system box, in turn, has a cabinet, a CPU, many RAM chips, and an optional fan.

      figure, multilevel Aggregation

Types of Aggregates

• Aggtegatopn can be fixed, variable or recursive
• A fixed aggtegate has a fixed structure; the number and types of subparts are predefined.

• A lamp has a fixed aggregate structure as shown in following figure.

          figure. Fixed aggregate

• A variable aggregate has a finite number of levels , but the number of parts may vary.
•   the company in following figure is a variable aggregate with two lelel tree structure. there are many division per company and many departments per division.

        figure. Variable Aggregation

• A recessive aggregate contains direcly or indirectly , an instance of the same kind of Aggregates; the number of potential levels is unlimited.
• Following figure shows the example of a computer program. A computer program is anh aggregation of blocks, with optionally recursive compound ststements; the recursion terminates with simplestatements. blocks csn be nested to arbitrary depth.

      Fig. Recursive Aggregation

Metadata

• Metadata is data that describes other data. it os also called data about data
• for example, in the dictionary we get gata about data, and hence it is an example of metadata
• The definition of a class id metadata because the class describes the objects
• Object models are inhetently metadata, since they describes the things being modeled
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